Design with natural stone cladding

Images courtesy of Picco Engineering

Written by Michael Biko, b.
The use of natural stone in buildings and paving can be traced back to the beginning of civilization. There are countless buildings, monuments, and structures dating back thousands of years that have stood the test of time and left generations in awe. Some examples of projects built primarily from local limestone include the Great Pyramid of Giza in Egypt, Mayan temples in Mexico, the round houses of Trulli in southern Italy, the Parthenon in Greece, and the Roman Amphitheater (which also included local limestone). Many of these great structures were built without mortar. The stones were simply cut, fitted together tightly, and dried stacked – a method of stone installation that has been imitated in modern construction and is referred to as “dry-stacked”.

In many ways, our predecessors in the construction industry applied sustainable practices by using larger quarry blocks to construct buildings and smaller pieces of waste to control erosion and driveways. They also used gravel to make small roads from one city to another.

When natural stone is selected and installed correctly, few cladding materials last a long time and perform well. It is not only aesthetically pleasing, but it is also a sustainable, low-maintenance material.

green stone
The inherent properties of natural stone make it a product for green building – it can be used without any additional finishing or wall coverings, it has low maintenance needs, and it is very durable. (This author acknowledges the assistance of Stephanie Vierra, Assoc. AIA, LEED AP [Vierra Design & Education Services LLC]in developing the article section on Stone and Sustainability Issues.) Unlike many cladding materials available on the market that require extensive manufacturing power, natural stone is ground, processed, chipped, finished, and chipped.

As more emphasis is placed on the entire building design and life cycle assessment, the concept of embodied energy for the product is an important and appropriate measure. Embodied energy is a measure of carbon dioxide (CO .).2) emitted from the time the raw materials are extracted to the point where they are installed on the building. This process has been referred to as “cradle to the gate”.

As building designs may use more materials (and/or more carbon-intensive products) to achieve lower energy use, an increasing proportion of the total energy use and carbon emissions of high-performance buildings come from their materials and products. By taking embodied energy into account, the project team can ensure that they are designing to reduce net carbon emissions. In the case of natural stone, this can include carbon dioxide2 Required during quarrying, transportation to factory, power required for tiles and fabrication, delivery to site, and installation. There is still some work being done by the various Life Cycle Analysis (LCA) authorities to establish definitions of what is and is not included in the accounts of different products to ensure a consistent and fair scale is established. However, based on most studies and comparisons, natural stone is consistently rated as one of the building materials with the lowest embodied energy in many scales.

Different materials, different stone
With the emergence of many new thin film cladding manufactured products put on the market, there is a recent trend for designers to define and detail extra large cladding panels. When using products such as porcelain, recycled glass, glass fiber reinforced concrete (GFRC), fiber-reinforced polymer (FRP), or engineered stone, care must be taken by architects and specifiers to clearly distinguish between natural and manufactured stone products. The design approach, attachment details and chassis can vary greatly.

This author has recently seen a trend to replace thinner engineered cladding product with thin and large natural stone slabs, with the erroneous assumption that they were essentially interchangeable. The versatility of natural stone requires a completely different design approach than manufactured products and, therefore, has different limitations associated with plate size and connection design.

New natural stones are continuously introduced to the market. Much of it is due to the discovery of new quarrying areas and stones, and many of them are the result of new technologies allowing to extract stones that were previously impossible to extract (described later in this article).

Some of these techniques include the use of injecting epoxy into the quarry with stones that have severe faults and cracks. In other cases, vacuum epoxy injection is used to stabilize cracked and severely cracked stone blocks. To the general consumer, these injections will be undetectable because they will only appear as another vein in the substance.

The epoxy present in the stone and the amount of sweating can have a significant impact on the technical properties of the stone. In most cases, the use of this severely filled and cracked material is limited to indoor use. Many of the highly sought-after, highly-scented onyx slabs on the market today are the result of these techniques. In the past, it was impossible to extract blocks large enough to produce panels as a single piece.

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